Control system for automatic vehicle transmissions

ABSTRACT

A system for controlling an automatic transmission of a vehicle, in which a pressure supply time to complete removal of the clutch-stroke play is determined based on the input shaft rotational speed. And a residual oil amount in the clutch is estimated and the time is corrected by the residual oil amount. The preparatory pressure to be supplied within the time is also determined based on the input shaft rotational speed and the ATF temperature. With this, it becomes possible to effect the clutch-stroke play removal within a less variant time and with a good response, thereby decreasing the shift shock effectively so as to improve the feeling of the vehicle occupant.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to a control system for an automaticvehicle transmission.

[0003] 2. Description of the Related Art

[0004] As a typical prior-art control system for automatic vehicletransmissions, Japanese Laid-Open Patent Application No. Hei 10 (1998) -184887 teaches supplying oil (ATF) at maximum hydraulic pressure (infull-duty) to a frictional engaging element such as a hydraulic clutchduring shift to remove the clutch-stroke play, thereby decreasing theshift shock experienced by the vehicle occupant.

[0005] Thus, in the prior art, since the oil at the line pressure isimmediately supplied to the clutch, this can advantageously shorten atime to complete removal of the clutch-stroke play. On the other hand,however, when the oil flow rate fluctuates due to the fluctuation of theengine speed or oil pump speed, the time to complete removal of theclutch-stroke play may disadvantageously varied. As a result, thetechnique may sometimes increase the shift shock until the learningcontrol correction has become effective.

BRIEF SUMMARY OF THE INVENTION

[0006] An object of this invention is therefore to overcome theaforesaid problem and to provide a control system for automatic vehicletransmission, which determines the time to complete removal of theclutch-stroke play of a frictional engaging element such as a hydraulicclutch based on at least the input shaft rotational speed such that theclutch-stroke play removal is effected within a less variant period oftime and with a good response, thereby decreasing the shift shockeffectively so as to improve the feeling of the vehicle occupant.

[0007] Another object of this invention is to overcome the aforesaidproblem and to provide a control system for automatic vehicletransmission, which determines a preparatory pressure to completeremoval of the clutch-stroke play of a frictional engaging element suchas a hydraulic clutch based on at lest the input shaft rotational speedsuch that the clutch-stroke play removal is effected within a lesservariant period of time and with a better response, thereby decreasingthe shift shock effectively so as to improve the feeling of the vehicleoccupant.

[0008] In order to achieve the objects, there is provided a system forcontrolling an automatic transmission of a vehicle having an input shaftconnected to an internal combustion engine mounted on the vehicle and anoutput shaft connected to driven wheels of the vehicle, the transmissiontransmitting input torque, through any of frictional engaging elements,generated by the engine and inputted by the input shaft to the drivenwheels by the output shaft, in accordance with predetermined shiftscheduling defining a target gear based on detected operating conditionsof the vehicle and the engine, comprising; input shaft rotational speeddetecting means for detecting an input shaft rotational speed inputtedto the transmission; supply time determining means for determining asupply time to supply a preparatory pressure to one of the frictionalengaging elements of the target gear to be shifted to, based on at leastthe detected input shaft rotational speed; oil amount estimating meansfor estimating an oil amount in the one of the frictional engagingelements; supply time correcting means for correcting the supply timebased on the estimated oil amount; preparatory pressure calculatingmeans for calculating the preparatory pressure to be supplied to the oneof the frictional engaging elements within the determined supply time;and hydraulic pressure control circuit for supplying the preparatorypressure to the one of the frictional engaging elements based on thecalculated preparatory pressure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] This and other objects and advantages of the invention will bemore apparent from the following description and drawings, in which:

[0010]FIG. 1 is an overall schematic view of a control system for anautomatic vehicle transmission according to the invention;

[0011]FIG. 2 is a main flow chart showing the operation of the systemillustrated in FIG. 1;

[0012]FIG. 3 is a flow chart showing the subroutine of conducting shiftcontrol referred to in the flow chart of FIG. 2;

[0013]FIG. 4 is a time chart showing the control points referred to inthe flow chart of FIG. 3;

[0014]FIG. 5 is a flow chart showing the subroutine of calculating theOFF-side desired clutch torque TQOF to be determined as a flat torque atthis stage;

[0015]FIG. 6 is a flow chart showing the subroutine of calculating theON-side clutch pressure QATON to be determined as a preparatory pressureat this stage and referred to in the flow chart of FIG. 3;

[0016]FIG. 7 is a graph showing the relationship between the manipulatedvariable and the a range of variance in calculating the pressurereferred to in the flow chart of FIG. 6;

[0017]FIG. 8 is a graph similarly showing the relationship between themanipulated variable and the range of variance in calculating thepressure referred to in the flow chart of FIG. 6;

[0018]FIG. 9 is a time chart showing the measurement of apreparation-completion time referred to in the flow chart of FIG. 6;

[0019]FIG. 10 is an explanatory time chart similarly showing themeasurement of the preparation-completion time referred to in the flowchart of FIG. 6, by changing a shift interval;

[0020]FIG. 11 is a graph showing the relationship between thepreparation-completion time and the shift interval illustrated in FIG.10;

[0021]FIG. 12 is a graph showing the preparation-completion timenormalized relative to the shift interval illustrated in FIG. 11;

[0022]FIG. 13 is a graph showing oil decreasing amounts relative to theshift interval obtained by converting the characteristics illustrated inFIG. 12;

[0023]FIG. 14 is a graph showing oil decreasing amounts relative to aresidual oil amount obtained by converting the characteristicsillustrated in FIG. 13;

[0024]FIG. 15 is an explanatory view of mapped data of the oildecreasing amount dOIL illustrated in FIG. 14, to be retrieved by theresidual oil amount, the input shaft rotational speed NM and the ATFtemperature;

[0025]FIG. 16 is a graph showing the oil decreasing amount, illustratedin FIG. 14, relative to the residual oil amount, the input shaftrotational speed NM and the direction of shift;

[0026]FIG. 17 is a graph showing characteristics, similar to thatillustrated in FIG. 16, of the prior art;

[0027]FIG. 18 is a flow chart showing the subroutine of calculating theON-side preparatory pressure QDB1A, etc. referred to in the flow chartof FIG. 6;

[0028]FIG. 19 is a flow chart showing the subroutine of estimating theresidual oil amount referred to in the flow chart of FIG. 18;

[0029]FIG. 20 is a flow chart showing the subroutine of calculating anOFF-side clutch pressure QATOF referred to in the flow chart of FIG. 3;

[0030]FIG. 21 is a flow chart showing the subroutine of calculating atorque-phase ON/OFF torques referred to in the flow chart of FIG. 3;

[0031]FIG. 22 is an explanatory time chart showing the operation of theflow chart of FIG. 21 and illustrating a reference value of themanipulated variable and a desired time in the inertia-phase inupshifting;

[0032]FIG. 23 is an explanatory time chart showing a tracking time onthe assumption that constant manipulated variable (pressure) A isapplied in the processing illustrated in FIG. 22;

[0033]FIG. 24 is an explanatory graph showing the response of themanipulated variable in the characteristics illustrated in FIG. 23;

[0034]FIG. 25 is a set of explanatory graphs showing comparison resultof the response of the manipulated variable illustrated in FIG. 24;

[0035]FIG. 26 is an explanatory graph showing a characteristic of atransient manipulate obtained by retrieving the manipulated variableillustrated in FIG. 24 by the response;

[0036]FIG. 27 is a flow chart showing the subroutine of calculating a G1torque TQUIA referred to in the flow chart of FIG. 21;

[0037]FIG. 28 is a flow chart showing the subroutine of calculating a Gttorque TQUTA1 referred to in the flow chart of FIG. 21;

[0038]FIG. 29 is a set of explanatory time charts showing parameters andvariables referred to in the flow charts of FIG. 27 and 28;

[0039]FIG. 30 is a flow chart showing the subroutine of calculatingtimes including a torque-phase control time TMDB2A referred to in theflow chart of FIG. 21;

[0040]FIG. 31 is a set of explanatory time charts showing thecalculation of the times including the torque-phase control time TMDB2Areferred to in the flow chart of FIG. 21;

[0041]FIG. 32 is a set of explanatory time charts similarly showing thecalculation of the times including the torque-phase control time TMDB2Areferred to in the flow chart of FIG. 21;

[0042]FIG. 33 is a block diagram showing the calculation of the enginetorque TTAP referred to in the flow chart of FIG. 21;

[0043]FIG. 34 is a time chart similarly showing the calculation of theengine torque TTAP referred to in the flow chart of FIG. 21;

[0044]FIG. 35 is a flow chart showing the subroutine of calculating theengine torque TTAP referred to in the flow chart of FIG. 21;

[0045]FIG. 36 is a flow chart showing the subroutine of calculating avalue DTEI referred to in the flow chart of FIG. 35;

[0046]FIG. 37 is a flow chart showing the subroutine of calculatingG1-G3 torques referred to in the flow chart of FIG. 3;

[0047]FIG. 38 is an explanatory graph showing a desired G (accelerationof gravity) acting in the longitudinal direction of the vehicle, onwhich the algorithm of the flow chart of FIG. 37 is based;

[0048]FIG. 39 is a set of explanatory graphs similarly showing thedesired G (acceleration of gravity) acting in the longitudinal directionof the vehicle, on which the algorithm of the flow chart of FIG. 37 isbased;

[0049]FIG. 40 is a time chart showing the processing in the flow chartof FIG. 37;

[0050]FIG. 41 is a time chart similarly, but partially showing theprocessing in the flow chart of FIG. 37;

[0051]FIG. 42 is a flow chart showing the subroutine of calculating G2torque TQUIA2 referred to in the flow chart of FIG. 37;

[0052]FIG. 43 is a flow chart showing the subroutine of calculating G3torque TQUIA3 referred to in the flow chart of FIG. 37;

[0053]FIG. 44 is a flow chart showing the subroutine of calculating anON-side engage pressure, more specifically, the subroutine oftorque-pressure conversion referred to in the flow chart of FIG. 3;

[0054]FIG. 45 is a set of graphs showing the torque-pressure conversionreferred to in the flow chart of FIG. 44;

[0055]FIG. 46 is a block diagram similarly showing the torque-pressureconversion referred to in the flow chart of FIG. 44; and

[0056]FIG. 47 is a flow chart showing the subroutine of calculating anON-side clutch pressure, more specifically, the subroutine oftorque-pressure conversion referred to in the flow chart of FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0057] An embodiment of the invention will now be explained withreference to the attached drawings.

[0058]FIG. 1 is an overall schematic view of a control system for anautomatic vehicle transmission according to the invention.

[0059] As shown in FIG. 1, a vehicle 1, illustrated partially by adriven wheel W (referred to later), etc., has an internal combustionengine E (referred to simply as “engine”) mounted thereon and anautomatic vehicle transmission T (referred to simply as “transmission”).The transmission T comprises the type of parallel-installed-shafts offive forward ratios.

[0060] Specifically, the transmission T is equipped with a main shaft(transmission input shaft) MS connected to a crankshaft 10 of the engineE through a torque converter 12 having a lockup mechanism L, and acountershaft CS provided in parallel with the main shaft MS. Theseshafts carry gears.

[0061] More specifically, the main shaft MS carries a main first gear14, a main second gear 16, a main third gear 18, a main fourth gear 20,a main fifth gear 22 and a main reverse gear 24. The countershaft CScarries a counter first gear 28 which meshes with the main first gear14, a counter second gear 30 which meshes with the main second gear 16,a counter third gear 32 which meshes with the main third gear 18, acounter fourth gear 34 which meshes with the main fourth gear 20, acounter fifth gear 36 which meshes with the main fifth gear 22 and acounter reverse gear 42 which meshes with the main reverse gear 24through a reverse idle gear 40.

[0062] In the above, 1st gear (first speed or gear ratio) is establishedor effected when the main first gear 14 rotatably mounted on the mainshaft MS is engaged with the main shaft MS by a first-gear hydraulicclutch C1. 2nd gear (second speed or gear ratio) is established when themain second gear 16 rotatably mounted on the main shaft MS is engagedwith the main shaft MS by a second-gear hydraulic clutch C2. 3rd gear(third speed or gear ratio) is established when the counter third gear32 rotatably mounted on the countershaft CS is engaged with thecountershaft CS by a third-gear hydraulic clutch C3.

[0063] 4th gear (fourth speed or gear ratio) is established when thecounter fourth gear 34 rotatably mounted on the countershaft CS isengaged with the countershaft CS by a selector gear SG and with thisstate maintained, the main fourth gear 20 rotatably mounted on the mainshaft MS is engaged with the main shaft MS by a fourth-gear/reversehydraulic clutch C4R. 5th gear (fifth speed or gear ratio) isestablished when the counter fifth gear 36 rotatably mounted on thecountershaft CS is engaged with the countershaft CS by a fifth-gearhydraulic clutch C5.

[0064] The reverse gear is established when the counter reverse gear 42rotatably mounted on the countershaft CS is engaged with thecountershaft CS by the selector gear SG and with this state maintained,the main reverse gear 24 rotatably mounted on the main shaft MS isengaged with the main shaft MS by the fourth-gear/reverse hydraulicclutch C4R.

[0065] The rotation of the countershaft CS is transmitted through afinal drive gear 46 and a final driven gear 48 to a differential D, fromwhere it is transmitted to the driven wheels W, through left and rightdrive shafts 50, 50 of the vehicle 1 on which the engine E and thetransmission T are mounted.

[0066] A shift lever 54 is installed on the vehicle floor near theoperator's seat to be manipulated by the vehicle operator to select onefrom among eight positions P, R, N, D5, D4, D3, 2 and 1.

[0067] A throttle position sensor (engine load detecting means) 56 isprovided in the air intake pipe (not shown) of the engine E at a pointin the vicinity of a throttle valve (not shown) and generates a signalindicative of the degree of throttle valve opening TH. A vehicle speedsensor 58 is provided in the vicinity of the final driven gear 48 andgenerates a signal indicative of the vehicle traveling speed V onceevery rotation of the final driven gear 48.

[0068] A crankshaft sensor 60 is provided in the vicinity of thecrankshaft of the engine E and generates a CYL signal once every apredetermined crank angular position of a predetermined cylinder, a TDCsignal at a predetermined crank angular position of each cylinder and aCRK signal at a predetermined crank angular position (such as 15 crankangles) obtained by dividing the interval between the TDC signals. Amanifold absolute pressure sensor 62 is installed in the air intake pipeof the engine E at a point in the vicinity of the throttle valve andgenerates a signal indicative of the manifold absolute pressure PBAindicative of the engine load.

[0069] A first rotational speed sensor 64 is provided in the vicinity ofthe main shaft MS and generates a signal indicative of the rotationalspeed NM of the transmission input shaft from the rotation of the mainshaft MS. A second rotational speed sensor 66 is provided in thevicinity of the countershaft CS and generates a signal indicative of therotational speed NC of the transmission output shaft from the rotationof the countershaft CS.

[0070] A shift lever position switch 68 is provided in the vicinity ofthe shift lever 54 and generates a signal indicating which of theaforesaid eight positions is selected by the vehicle operator. An oiltemperature sensor 70 is installed in the transmission T or at anappropriate location close thereto and generates a signal indicative ofthe oil temperature, i.e., the temperature TATF of AutomaticTransmission Fluid. And a brake switch 72 is provided in the vicinity ofa brake pedal (not shown) and generates an ON signal when the brakepedal is depressed by the vehicle operator.

[0071] The outputs of the sensors 56, etc., are sent to an ECU(electronic control unit) 80. The ECU is constituted as a microcomputercomprising a CPU (central processing unit) 82, a ROM (read-only memory)84, a RAM (random access memory) 86, an input circuit 88, an outputcircuit 90 and an A/D converter 92. The outputs of the sensors 56, etc.,are inputted to the microcomputer from the input circuit 88.

[0072] The analog outputs of the sensors are converted into digitalvalues through the A/D converter 92 and are stored in the RAM 86, whilethe digital outputs of the sensors are processed by a processing circuitsuch as a wave-form shaper (not shown) and are similarly stored in theRAM 86.

[0073] The outputs of the vehicle speed sensor 58 and the CRK signaloutputted by the crank angle sensor 60 are inputted to a counter (notshown) to be counted to determine the vehicle speed V and the enginespeed NE. Similarly, the outputs of the first and second rotationalspeed sensors 64, 66 are counted by the counter to determine the inputshaft rotation speed NM and the output rotation speed NC of thetransmission T.

[0074] The CPU 82 of the microcomputer determines the (target) gear(gear ratio) to be shifted to and energizes/deenergeizes shift solenoidsSL1 to SL5 (each comprises an electromagnetic solenoid) of a hydraulicpressure control circuit O, through the output circuit 90 and a voltagepressure circuit (not shown), to control the supply of the hydraulicpressure to the clutches (frictional engaging elements) such that theshift is effected, and energizes/deenergizes linear solenoids SL6 to SL8(each comprises an electromagnetic solenoid) to control the operation ofthe lockup clutch L of the torque converter 12.

[0075] The operation of the control system of an automatic vehicletransmission according to the invention will be explained.

[0076]FIG. 2 is a flow chart showing the operation of the system. Theprogram illustrated here is executed once every 10 msec.

[0077] Explaining this, the program begins in S10 in which a known shiftmap (shift scheduling map; not shown) is retrieved using the detectedvehicle speed V and the throttle opening TH, and proceeds to S12 inwhich the retrieved value is determined to be a target gear (to beengaged with or shifted to) SH. The program then proceeds to S14 inwhich the current gear (now being engaged) is rewritten as or named GAand the target gear SH is rewritten as or renamed GB.

[0078] The program then proceeds to S16 in which QATNUM (indicative ofshift mode) is read. The shift mode QATNUM is prepared in a memory ofthe RAM 86 (or ROM 84) and indicates the mode of shift. Specifically, itis expressed, for example, as 11 h (indicating upshift from 1st to 2ndgear), 12 h (indicating upshift from 2nd to 3rd gear), 21 h (indicatingdownshift from 2nd to 1st), 31 h (indicating that 1st gear should beheld). More specification, the first numeral of the shift mode QATNUMindicates the mode of shift as 1: upshifting, 2: downshifting and 3:holding current gear. In the below, it will be mentioned that whetherthe shift mode QATNUM is 1 * h, for example. This means that it shouldbe determined that the shift is, whichever the gear is, upshifting.

[0079] The program then proceeds to S18 in which SFTMON (indicative ofshift monitor) is initialized to 0, when it is determined that shiftcontrol is needed from the processing in S10 and on. The SFTMON isprepared in a memory of the RAM 86 (or ROM 84) and indicates the time ofthe shift control. The program then proceeds to S20 in which the shiftcontrol is conducted, if needed. If the first numeral of the shift modeQATNUM is 3, the current gear is held and no shift control isimplemented.

[0080]FIG. 3 is a flow chart showing the subroutine of the shift controlreferred to in S20 of FIG. 2. The program illustrates the shift controltaking the upshift as an example of the shift.

[0081] In the below, the shift control is explained with respect to theupshift, more specifically the upshift from 1st to 2nd gear. In otherwords, it is assumed that the current gear GA is 1st and the target gearGB is 2nd.

[0082] Explaining the upshift control illustrated in the flow chartreferring to a time chart shown in FIG. 4, the program begins in S100 inwhich it is determined whether the bit of the aforesaid value SFTMON is0. Since the value has been initialized to 0 in S18, the result isaffirmative and the program proceeds to S102 in which initialization isconducted such that parameters or variables including a desired clutchtorque as well as timer or counter values (all explained later) are allinitialized. The program then proceeds to S104 in which the value ofSFTMON is set to 10 h.

[0083] The program then proceeds to S106 in which, since it is a time tostart preparation of shift control as illustrated in the time chart ofFIG. 4, an ON-side desired clutch torque for the target gear to beshifted to, hereinafter referred to as “TQON”, i.e. for the 2nd clutchC2 which effects the target gear (2nd gear), is set to 0, and to S108 inwhich an OFF-side flat torque is calculated as an OFF-side desiredclutch torque (for the current gear (i.e. 1st clutch C1) to bereleased), hereinafter referred to as “TQOF”, at this stage, such thatthe engine torque is maintained.

[0084] In the specificate and figures, the term “ON-side” indicates theclutch to be engaged (i.e., that for the target gear) and the term“OFF-side” indicates the clutch to be relieved or disengaged (i.e. thatfor the current gear). And the word “flat” indicates a flat portion inthe wave-form of the hydraulic pressure or torque.

[0085]FIG. 5 is a flow chart showing the subroutine for calculating theOFF-side desired clutch torque TQOF to be determined as a flat torque atthis stage.

[0086] In S200, an available additive torque value #dTQUTRF is added tothe engine torque (more precisely an estimated input torque; explainedlater) TTAP and the sum is defined as the OFF-side desired clutch torqueTQOF.

[0087] Returning to the explanation of the flow chart of FIG. 3, theprogram proceeds to S110 in which an ON-side preparatory pressure iscalculated as an ON-side clutch pressure for the clutch (C2) foreffecting the target gear to be engaged, referred to as “QATON”, at thisstage. This corresponds to fill a clutch-stroke play with oil andremoving the play.

[0088]FIG. 6 is a flow chart showing the subroutine for calculating theON-side clutch pressure QATON to be determined as the preparatorypressure at this stage.

[0089] Before entering the explanation of the flow chart, thecalculation of the ON-side clutch pressure (as the preparatory pressurefor removing the clutch-stroke play) in the system of the embodimentwill be explained.

[0090] Briefing the system, the aforesaid prior art teaches supplyingoil (ATF) at maximum hydraulic pressure (in full-duty) to a frictionalengaging element such as a hydraulic clutch during shift to remove theclutch-stroke play, thereby decreasing the shift shock experienced bythe vehicle occupant.

[0091] Thus, in the prior art, since the oil at the line pressure isimmediately supplied to the clutch, this can advantageously shorten atime to complete removal of the clutch-stroke play. On the other hand,however, when the oil flow rate fluctuates due to the fluctuation of theengine speed or oil pump speed, the time to complete removal of theclutch-stroke play may disadvantageously varied. As a result, thetechnique may sometimes increase the shift shock until the learningcontrol correction has become effective.

[0092] In view of the above, the system of this embodiment is configuredthe time to complete removal of the clutch-stroke play, i.e. the supplytime (during which the supply of hydraulic pressure is continued) andthe preparatory pressure therefor are determined based on the rotationalspeed of the clutch concerned (i.e. 2nd clutch C2 in this case) and theATF temperature.

[0093] The supply time varies depending upon various factors such as themanipulated variable (supplied pressure), the clutch rotational speed,the ATF temperature, a shift interval (an interval between a time pointat which the manipulated variable was made zero for a given clutch and atime point at which the manipulated variable is again given for the sameclutch), the position of the clutch (height or distance from thereservoir in the drainage), the length of passage for supply anddraining oil, the number of shift valves involved, the characteristicsof the shift solenoid(s) (actuator(s)) SLn, and the manufacturingvariance of the clutch (such as volume, the spring constant, etc).

[0094] In view of the above, in the system, from among the factors, theposition of the clutch, the length of passage for supply and drainingoil and the number of shift valves involved are predetermined in advancefor respective clutches and stored in a memory of the ROM 84 (or RAM86), while the characteristics of the shift solenoid(s), themanufacturing variance of the clutch, etc. are to be compensated in theentire system of the shift control.

[0095] The compensation in the entire system of the shift control willbe explained.

[0096] Since a time necessary for completing or finishing thepreparation (preparation-completion time) decreases as the manipulatedvariable (QATON) increase, it will be effective to determine themanipulated value to an increased amount. However, as illustrated inFIG. 7, the range of variance increases with increased manipulatedvariable (shown as “Q1” in FIGS. 7 to 9), which degrades the controlaccuracy. For this reason, as illustrated in FIG. 8, the manipulatedvariable (and the shift interval) are to be predetermined in advance ina narrow range marked by A such that both the control accuracy andcontrol response are satisfied.

[0097] Then, with respect to the manipulated variable and the shiftinterval thus predetermined, as illustrated in FIG. 9, by measuring thepreparation-completion time T by changing the clutch rotational speed(input shaft rotational speed NM) and the ATF temperature, it becomespossible to collect data necessary for the respective clutches. Andusing the collected data as a base, as regards the shift interval, aresidual oil amount (the residual amount of ATF or oil in the clutch) isestimated and the preparation-completion time T is corrected by theestimated residual oil amount.

[0098] Explaining the data collection, as illustrated in FIG. 10, thepreparation-completion time T is measured by changing the shift intervalXn (shown as “X1” “X2” “Xn” in the figure). Then, graphing therelationship between the shift interval (generally expressed as “Xn”)and the preparation-completion time T as illustrated in FIG. 11, thepreparation-completion time T is normalized between 0 (in-clutch oilempty) and 1 (in-clutch oil full) relative to the shift interval Xn, asillustrated in FIG. 12.

[0099] Then, as illustrated in FIG. 13, an oil decreasing amount (oildecreasing rate) relative to the shift interval Xn is calculated and isgraphed. Then, as illustrated in FIG. 14, the oil decreasing amountrelative to the shift interval is converted into an oil decrease amount(oil decreasing rate) relative to the residual oil amount. The oildecreasing amount is hereinafter referred to as “dOIL”.

[0100] Specifically, the values (i.e. slopes) relative to the residualoil amount illustrated in FIG. 13 is retrieved each time a predeterminedperiod of time has elapsed (i.e., each time the program is looped) sincethe manipulated variable was made zero, and the retrieved value issuccessively subtracted from the residual oil amount. Accordingly, whenthe manipulated variable is kept zero for a relatively long period oftime, the residual oil amount will be estimated to be zero.

[0101] Then, as illustrated in FIG. 15, the oil decreasing amount dOILrelative to the residual oil amount and the input shaft rotational speedNM is prepared as mapped data with respect to the ATF temperaturesTATF1, 2, . . . n. Thus, by retrieving the mapped data, it becomespossible to determine the change of the residual oil amount relative tothe change of the input shaft rotational speed NM, as shown in FIG. 16.

[0102] To be more specific, as illustrated in FIG. 17 with B, if theresidual oil amount were stored relative to the shift interval Xnsolely, it would discontinuously change to and fro in the direction oftime. As a result, it would be quite difficult to determine the residualoil amount change relative to the change of the input shaft rotationalspeed because of the difficulty in tracking the rotational speed change.However, having been configured in the above, it becomes possible todetermine the residual oil amount relative to the change of the inputshaft rotation speed NM.

[0103] Thus, the system is configured such that, thepreparation-completion time T when the residual oil amount is zero isstored in a memory and the residual oil amount OILn from the oildecreasing amount dOIL is calculated, and based thereon, an actualpreparation-completion time (control time; referred to as “T1”) is to becalculated. In the residual oil amount OILn, n is one from among 1 to 5and indicates the residual oil amount in any of the five clutchescorresponding to the number.

[0104] Based on the above, the calculation of the ON-side clutchpressure QATON (as the preparatory pressure at this stage) will beexplained with reference to the flow chart of FIG. 6.

[0105] The program begins in S300 in which it is determined whether thevalue of SFTMON is 10 h. Since it has been set to 10 h in S104 in theflow chart of FIG. 3, the result is affirmative and the program proceedsto S302 in which the value of SFTMON is rewritten as 11 h. The programthen proceeds to S304 in which the ON-side preparatory pressure(hereinafter referred to as “QDB1A” (for the 2nd clutch C2 in this case)and the aforesaid actual preparation-completion time T1 are retrieved.

[0106]FIG. 18 is a flow chart for the subroutine of the retrieval.

[0107] The program begins in S400 in which the actualpreparation-completion time TI is retrieved from mapped data (whosecharacteristics are not illustrated) using the detected input shaftrotational speed NM and the ATF temperature TATF as address data. Theprogram then proceeds to S402 in which the preparatory pressure QDB1A isretrieved from mapped data (whose characteristics are not illustrated)using the same parameters as the address data. The program then proceedsto S404 in which the aforesaid residual oil amount OILn is estimated.

[0108]FIG. 19 is a flow chart showing the subroutine for the estimation.

[0109] The program is executed separately for the five clutches C1 toC5. Although, for the purpose of brevity, general explanation will bemade taking the 2nd clutch C2 as an example, that will similarly beapplied to the other four clutches.

[0110] The program begins in S500 in which it is determined whether thevalue of a timer tmST (down-counter) is 0. The value of timer is resetto 0 in S102 in the flow chart of FIG. 3, when the shift is not inprogress, in other words, when the value of SFTMON is 0 in the timechart of FIG. 4.

[0111] When the result in S500 is affirmative, the program proceeds toS502 in which it is determined whether the target gear GB is 2nd. Whenthe result is affirmative, since the shift is not in progress such thatthe 2nd clutch C2 is engaged (made ON), the program proceeds to S504 inwhich the residual oil amount OIL2 (the residual oil amount in 2ndclutch C2 (preceding value)) is determined to be 1, in other words, itis estimated that the second clutch C2 is filled with oil.

[0112] When the result in S502 is negative, the program proceeds to S506in which it is determined whether the residual oil amount (of the secondclutch C2) OIL2 is less than a predetermined value #OILMIN. When theresult is affirmative, the program proceeds to S508 in which it isestimated that the residual oil amount (preceding value) is 0, in otherwords, it is estimated that the second clutch C2 is empty.

[0113] On the other hand, when the result in S506 is negative, theprogram proceeds to S510 in which the oil decreasing amount dOIL2 isretrieved from one from among mapped data (which are prepared separatelyfor the ATF temperature TATF and the length of oil passage for supplyand drainage of the clutch concerned) using the detected input shaftrotational speed NM and the residual oil amount OIL2. The program thenproceeds to S512 in which the oil decreasing amount dOIL2 is subtractedfrom the residual oil amount OIL2 to correct the same.

[0114] When the result in S500 is negative, since this indicates thatthe shift is in progress, the program proceeds to S514 in which it isdetermined whether the target gear GB is 2nd. When the result in S514 isaffirmative, the program proceeds to S516 in which it is determinedwhether the current gear GA is 2nd and the manipulated variable(OFF-side clutch pressure QATOF) is greater or equal to a predeterminedvalue #QDB1MIN. When the result is affirmative, the program proceeds toS518 in which the residual oil amount OIL2 is determined to be 1.

[0115] When the result in S516 is negative, the program proceeds to S520in which it is determined whether the residual oil amount OIL2 is lessthan the predetermined value #OILMIN. When the result is affirmative,the program proceeds to S522 in which the residual oil amount OIL2 isdetermined to be 0. When the result in S520 is negative, the programproceeds to S524 in which the oil decreasing amount dOIL2 is retrievedfrom the mapped data in the manner similar to that explained in S510,and to S526 in which the residual oil amount OIL2 is corrected in themanner similar to that explained in S512.

[0116] When the result in S514 is negative, the program proceeds to S528in which it is determined whether the shift mode QATNUM is 1 * h and thevalue of a timer tUPA1 (corresponding to the preparation-completiontime) is not 0, in other words, it is determined whether the upshift isin progress. When the result is affirmative, the program proceeds toS530 in which a quotient (obtained by dividing the residual oil amountOIL2 by the timer value tUPA1) is added to the residual oil amount OIL2to correct the same.

[0117] When the result in S528 is negative, the program proceeds to S532in which it is determined whether the shift mode QATNUM is 2 * h and thevalue of a timer tKPAJ is 0, in other words, it is determined whetherthe downshift is in progress. When the result is affirmative, theprogram proceeds to S534 in which a quotient (obtained by dividing theresidual oil amount OIL2 by the timer value tKPAJ) is added to theresidual oil amount OIL2 to correct the same. When the result in S532 isnegative, the program proceeds to S536 in which the residual oil amountOIL2 is determined to be 1.

[0118] Returning to the explanation of the flow chart of FIG. 18, theprogram proceeds to S406 in which the actual preparation-completion timeT1 is multiplied by the determined residual oil amount OILn to correctthe same.

[0119] Returning to the explanation of the flow chart of FIG. 6, theprogram proceeds to S306 in which the determined actualpreparation-completion time T1 is set on the timer tUPA1 to start timemeasurement. The program then proceeds to S308 in which the determinedON preparation pressure QDB1A is determined to be the ON-side clutchpressure QATON. This is the same when the result in S300 is negative.

[0120] Having been configured in the foregoing manner, the systemaccording to the embodiment can determine the manipulated variable andthe control time with a less variance and good control response, inresponse to the rising of the clutch pressure. Moreover, by estimatingthe residual oil amount (residual oil amount in the clutch) and bycorrect the control time by the estimated value, the system can realizean appropriate control even for continuous shifting.

[0121] Returning to the explanation of the flow chart of FIG. 3, theprogram proceeds to S112 in which an OFF-side flat pressure iscalculated or determined as the OFF-side clutch pressure QATOF.

[0122]FIG. 20 is a flow chart for the subroutine of the calculation.

[0123] The program begins in S600 in which the OFF-side desired clutchtorque TQOF is calculated as a lower limit value in an appropriatemanner and proceeds to S602 in which the calculated value is determinedto be the OFF-side clutch pressure QATOF.

[0124] Again returning to the flow chart of FIG. 3, in the next programloop, it is determined in S100 whether the value of SFTMON is 0. Sincethe value was set to 10 h in S104 in the last program loop, the resultin S100 is normally negative and the program proceeds to S114 in whichit is determined whether the value of SFTMON is 10 h or 11 h (shown inFIG. 4).

[0125] When the result in S114 is affirmative, the program proceeds toS116 in which it is determined whether the value of the timer tUPA1(indicative of the actual preparation-completion time T1) has reached 0.When the result is negative, since this indicates the time has notelapsed, the program proceeds to S106. On the other hand, when theresult is affirmative, the program proceeds to S118 in which the valueof SFTMON is rewritten as 20 h. The program then proceeds to S120 inwhich a torque-phase ON/OFF torque calculation is conducted.

[0126]FIG. 21 is a flow chart showing the subroutine for thecalculation.

[0127] Before entering the explanation, the calculation will be briefed.

[0128] In the embodiment, the system is configured to determine a timeto track (follow up) the pressure rise of the clutch to be engaged(ON-side) after completion of preparation and the characteristic oftorque resulting in therefrom, based on data stored in a memory of theROM 84 (or RAM 86) of the ECU 80. Here, the tracking (follow-up) timeindicates a period of time until the actual hydraulic pressure reaches acommand value since the beginning of the torque rise.

[0129] With this, the system can recognize from when and how the ON-sideclutch generates the torque, and based on the recognized torque and theestimated input torque (engine torque), it can calculate the pressurenecessary for the OFF-side clutch. Saying this simply, the system isconfigured to determine the OFF-side value such that it balances withthe input to the ON-side.

[0130] Specifically, in the upshift control, the pressure to be suppliedin the inertia-phase is normally determined in order to decrease theshift shock. In the system, if defining a reference value of the desiredmanipulated variable (indicative of the pressure to be supplied) by X,the system is configured to determine a transient value of themanipulated variable in the following such that the actual clutch(hydraulic) pressure becomes equal to that determined by the referencedesired manipulated variable X within a predetermined desired time Y, asillustrated in FIG. 22.

[0131] More specifically, as illustrated in FIG. 23, a tracking time Bis obtained beforehand through experimentation, on the assumption thatconstant (hydraulic) pressure (manipulated variable A) is applied and isstored in the memory as a slope K (=A/B). The manipulated variable Acomprises a plurality of values selected from those that actually usedin the shift control and is stored as mapped data (first data) X1(n) tobe retrieved by the input shaft rotational speed NM and the ATFtemperature TATF.

[0132] Moreover, as illustrated in FIG. 24, the slope K is also storedas mapped data (second data). The slope K can indicate a controlresponse of the manipulated variable A which realizes the actualpressure reaching the command value within a certain period of time whenoutputted.

[0133] Then, the ratio between the values X and Y (=X/Y; hereinafterreferred to as “KX”) is determined. Then, defining the ratio KX as adesired value, the ratio KX is compared with K (the second dataindicative of the response of A), as illustrated in FIG. 25A. When K>KX,since this indicates that the stored data is greater, in other words,since this indicates that it is possible to reach the reference desiredmanipulated variable X within the desired time Y, the desired value KXis determined to be the slope to be executed (determined value;hereinafter referred to as “KZ”), as illustrated in FIG. 25B.

[0134] On the other hand, when K<KX, since this indicates that thedesired slope is greater, in other words, since this indicates that itis not possible to reach the reference desired manipulated variable Xwithin the desired time Y, the time is extended to Y1 and the mappeddata K is determined to be the slope (to be executed) KZ, as illustratedin FIG. 25C.

[0135] Then, the manipulated variable A is determined by retrieving themapped data (second data) illustrated in FIG. 26. More concretely, themanipulated variable X1(n) is retrieved from the mapped data using thedetermined slope KZ as address datum. When K<KX, since it is notnecessary to continuously output the reference desired manipulatedvariable X during the desired period of time, the value X1 becomes lessthan the value X. On the other hand, when K>KX, the values X and X1become close to each other.

[0136] With respect to the desired time, the time Y1 is determined asY1=X/KZ. When KZ=KX, Y=Y1. When KZ<KX, as illustrated in FIG. 25C,Y1=(X/KZ)> Y. This indicates that, when it is impossible to completewithin the desired time, the execution time is automatically extendedbased on the eigenvalue of the mechanic system in the prepared data.

[0137] On the other hand, when KZ>KX, as illustrated in FIG. 25B, X1 isoutputted as a transient pressure (manipulated variable) so as to bringthe pressure to the desired value just within the desired time, the timeY1 for outputting X1 can be determined as Y1=X1/KZ.

[0138] Based on the above, the calculation of the torque-phase ON/OFFtorques will be explained with reference to the flow chart of FIG. 21.

[0139] The program begins in S700 in which a G1 torque TQUIA1 iscalculated. The G1 torque indicates a desired torque at the beginning ofthe inertia-phase and is calculated based on a desired value of theacceleration of gravity (hereinafter referred to as “G”) in the lineardirection. G2 torque and G3 torque explained later are similar desiredtorques at the midpoint and terminal point of the inertia-phase.

[0140]FIG. 27 is a flow chart showing the subroutine for thecalculation.

[0141] The program begins in S800 in which it is determined whether thevalue of SFTMON is 20 h. Since it was set to 20 h in S118 in the flowchart of FIG. 3, the result is naturally affirmative and the programproceeds to S802 in which the detected vehicle speed V is fixed and thefixed value is named a predetermined vehicle speed VUTA such that thesame vehicle speed should be used in calculating the G2 torque and theG3 torque.

[0142] The program then proceeds to S804 in which it is determinedwhether the estimated input torque (engine torque) TTAP is greater orequal to 0. When the result is negative, the program proceeds to S806 inwhich the G1 torque TQUIA1 is determined to be a predetermined value#dTQUIAM (value indicative of the available torque such as 3 kgf.m).

[0143] When the result in S804 is affirmative, the program proceeds toS808 in which it is determined whether a product obtained by multiplyingthe estimated input torque TTAP by a ratio or correction coefficient#kGUIA1 (obtained by the predetermined (fixed) vehicle speed VUTA andthe throttle opening) and by a difference (between the gear ratio(#RATIOn/#RATIOm) and 1.0), is greater than the predetermined value#dTQUIAM.

[0144] When the result in S808 is negative, the program proceeds to S812in which a sum (obtained by adding the predetermined value #dTQUIAM isadded to the estimated input toque TTAP) is determined to be the G1torque TQUIA1. When the result in S808 is affirmative, the programproceeds to S810 in which the G1 torque TQUIA1 is calculated as follows:

TQUIA1=TTAP * {1+#kGUIA1* ((#RATIOn/#RATIOm)−1)}

[0145] The G1 torque and the ratio (correction coefficient #kGUIA1 willlater be referred to. In the above equation and other equations, thesymbol “*” indicates multiplication.

[0146] Returning to the explanation of the flow chart of FIG. 21, theprogram proceeds to S702 in which a Gt torque TQUTA1 is calculated. TheGt torque TQUTA1 indicates a desired torque at the terminal point of thetorque phase.

[0147]FIG. 28 is a flow chart showing the subroutine of the calculation.

[0148] The program begins in S900 in which it is determined whether theestimated input torque TTAP is greater or equal to 0, and if the resultis affirmative, the program proceeds to S902 in which the estimatedinput torque TTAP is multiplied by a predetermined value #kGUTA1 and theproduct is determined to be a desired torque tqutal. When the result inS900 is negative, the program proceeds to S904 in which the desiredtorque tqutal is determined to be 0.

[0149] The program then proceeds to S906 in which it is determinedwhether the value of SFTMON is 20 h. When the result is affirmative,since this indicates that the current program loop is for the first timein the torque-phase, the program proceeds to S908 in which the Gt torqueTQUTA1 is determined to be the desired torque tqutal.

[0150] On the other hand, when the result in S906 is negative, theprogram proceeds to S910 in which it is determined whether the desiredtorque tqutal is greater or equal to the Gt torque TQUTA1. When theresult is affirmative, since this the value is greater or equal to thepreceding value, the program is immediately terminated so as not toupdate the value. When the result is negative, the program proceeds toS912 in which the desired torque tqutal is determined to be the Gttorque TQUTA1.

[0151]FIGS. 29A, 29B and 29C illustrate the parameters and variablesused in the flow charts of FIG. 27 and 28.

[0152] Returning to the flow chart of FIG. 21, the program proceeds toS704 in which it is determined whether the value of SFTMON is 20 h, inother words, it is determined whether the program loop is for the firsttime in the torque-phase. When the result is affirmative, the programproceeds to S706 in which the value of SFTMON is set to 21 h and to S708in which the Gt torque TQUTA1 is converted into a pressure value namedGt pressure QUTA1.

[0153] The program then proceeds to S710 in which a minimum pressureQUIAL for the clutch to be engaged (ON-side). The program then proceedsto S712 in which a predetermined value #TMUTAG is retrieved which isdetermined to be a torque-phase desired time TMUTAG. The program thenproceeds to S714 in which various values including a torque-phasecontrol time for the ON-side clutch in upshift named TMDB2A (thetracking time to the desired value), a torque-phase boost pressure QDB2A(corresponding to X1(a) in FIG. 25B) and a boost control time TMDB2B(corresponding to Y in FIG. 25B) are calculated.

[0154]FIG. 30 is a flow chart showing the subroutine for the calculationand FIGS. 31 and 32 are time charts showing the torque-phase timeTMDB2A, etc.

[0155] The program begins in S1000 in which it is determined whether theGt pressure QUTA1 is greater than the ON-side minimum value QUIAL, andwhen the result is affirmative, the program proceeds to S1002 in which areached-pressure qutal (corresponding to X mentioned with reference toFIG. 22) is determined to be the Gt pressure QUTA1. When the result inS1000 is negative, the program proceeds to S1004 in which thereached-pressure qutal is determined to be the minimum pressure QUIAL.

[0156] The program then proceeds to S1006 in which a torque-phasemaximum (steepest) slope kDB2A (corresponding to the aforesaid Kmentioned with reference to FIG. 25A) is retrieved from mapped databased on the shift mode QATNUM using the detected input shaft rotationalspeed NM, the reached-pressure qutal and the ATF temperature TATF asaddress data. The program then proceeds to S1008 in which thereached-pressure qutal is divided by the aforesaid value TMUTAG(torque-phase desired time (desired reaching time); corresponding to theaforesaid Y mentioned with reference to FIG. 22) and the obtainedquotient is determined to be a torque-phase slope kDB2B (correspondingto the aforesaid KX described with reference to FIG. 25A). FIG. 32Aillustrates the torque-phase desired time TMUTAG, etc.

[0157] The program then proceeds to S1010 in which it is determinedwhether the determined torque-phase slope kDB2B is greater than thetorque-phase maximum slope kDB2A. When the result is affirmative, sincethis indicates that the torque-phase time is extended and the programproceeds to S1012 in which the torque-phase maximum slope kDB2A isdetermined to be a slope k. On the other hand, when the result isnegative, the program proceeds to S1014 in which the torque-phasemaximum slope kDB2B is determined to be the slope k.

[0158] The program then proceeds to S1016 in which the boost pressureQDB2A is retrieved from mapped data based on the shift mode QATNUM usingthe detected input shaft rotational speed NM, the slope k and the ATFtemperature TATF as address data. The program then proceeds to S1018 inwhich the reached- pressure qutal is divided by the slope k and theobtained quotient is determined to be the torque-phase control timeTMDB2A.

[0159] The program then proceeds to S1020 in which the boost pressureQDB2A is divided by the slope k and the obtained quotient is determinedto be the boost control time TMDB2B. The program then proceeds to S1022in which a break time TMDB2C is retrieved from mapped data based on theshift mode QATNUM using the detected input shaft rotational speed NM,the boost pressure QDB2A and the ATF temperature TATF as address data.

[0160] Returning to the explanation of the flow chart of FIG. 21, theprogram proceeds to S716 in which the calculated torque-phase controltime TMDB2A, the boost control time TMDB2B and the break time TMDB2C arerespectively set on timers tUTAG, tUTA1 and tUTA2 to start timemeasurement. The program then proceeds to S718 in which the calculatedboost pressure QDB2A is converted into a torque value TQUTAB in anappropriate manner.

[0161] The program the proceeds to S720 in which the ON-side desiredclutch torque TQON is made 0, to S722 in which an available additivetorque value #dTQUTRF is added to the estimated input torque TTAP andthe sum is determined to be the OFF-side desired clutch torque TQOF.

[0162] On the other hand, when the result in S704 is negative, theprogram proceeds to S724 in which it is determined whether the value ofSFTMON is 21 h. When the result is affirmative, the program proceeds toS726 in which it is determined whether the value of the timer tUTA2 (setwith TMDB2C) is 0 and if the result is negative, since this indicatesthat it is before the break, as shown in FIG. 31A, the program proceedsto S720.

[0163] When the result in S726 is affirmative, the program proceeds toS728 in which the value of SFTMON is set to 22 h, and proceeds to S730in which the ON-side desired clutch torque TQON is calculated byinterpolating TQUTA1, etc., as shown there and in FIG. 31B. The programthen proceeds to S732 in which the ON-side desired clutch torque TQON issubtracted from the values shown there and the difference is determinedto be the OFF-side desired clutch torque TQOF.

[0164] When the result in S724 is negative, the program proceeds to S734in which it is determined whether the value of SFTMON is 22 h. When theresult is affirmative, the program proceeds to S736 in which it isdetermined whether the value of the timer tUTA1 is 0. When the result isnegative, the program proceeds to S730. When the result is affirmative,the program proceeds to S738 in which the value of SFTMON is set to 23h. When the result in S734 is negative, the program proceeds to S740.

[0165] The program then proceeds to S740 in which the ON-side desiredclutch torque TQON is calculated by interpolating a portion betweenTQUTAB and TQUTA1 as shown there and in FIG. 31C, and proceeds to S742in which the OFF-side desired clutch torque TQOF is calculated in themanner as shown and similar to that mentioned in S732.

[0166] Having been configured in the foregoing manner, the systemaccording to the embodiment can effect the control taking the trackingof hydraulic pressure into account and can track the change of theestimated input torque, without causing the engine to rev over orexcessively. Moreover, it can shorten the torque-phase control time andrealize an improved control which can effectively suppress the shiftshock.

[0167] Returning to the explanation of the flow chart of FIG. 3, theprogram proceeds to S122 in which the ON-side torque-phase pressure iscalculated or determined as the ON-side clutch pressure QATON, and toS124 in which the OFF-side torque-phase pressure is calculated ordetermined as the OFF-side clutch pressure QATOF in the mannerillustrated in FIG. 20.

[0168] When the result in S114 is negative, the program proceeds to S126in which it is determined whether the value of SFTMON is 20 h or 21 h.When the result is affirmative, the program proceeds to S128 in which itis determined whether the value of the timer tUTAG is 0 and when theresult is negative, the program proceeds to S120. When the result inS128 is affirmative, the program proceeds to S130 in which the value ofSFTMON is set to 30 h.

[0169] Here, the calculation or estimation of the engine torque(estimated input torque) will be explained.

[0170] Conventionally, as taught in Japanese Laid-Open PatentApplication No. Hei 6 (1994) - 207660, the engine toque is estimatedbased on the vehicle speed and the throttle opening. Alternatively, itis estimated from information including the engine speed and manifoldabsolute pressure or from the state of the torque converter, etc.

[0171] However, when the engine torque is estimated from the throttleopening, etc., the estimation is likely to be affected by the change inenvironment. When it is estimated from the manifold absolute pressure,etc., since factors of the torque converter and inertia energy are nottaken into account, the estimation accuracy is not always satisfactory.Further, when it is estimated from the state of the torque converter,since the toque absorption characteristic of the torque converterchanges suddenly when fully-locked up or thereabout, the estimationaccuracy is liable to be degraded particularly in a transient state.

[0172] In view of the above, as illustrated in FIG. 33, based on mappeddata of the engine torque TEPB retrievable by the engine speed NE andthe manifold absolute pressure PBA, the system according to theembodiment calculate a value indicative of inertia torque DTEI used forraising the engine speed NE therefor, and calculates or estimates theinput torque TTAP using the calculated the value DTEI and a torqueconverter torque ratio KTR.

[0173] Specifically, the input torque TTAP is calculated as follows:

TTAP=(TEPB−DTEI) * KTRLAT

[0174] The value DTEI is set to zero if a torque converter slip ratioETR is greater than 1.0, in other words, if it is driven by the vehiclewheels. The value DTEI is smoothed to be prepared for the use in theupshift. Moreover, if a shift starts when the upshift is in progress,the engine speed NE drops and the value DTEI becomes negative. However,since the engine torque remains unchanged, the system is configured notto calculate the inertia torque when the shift is in progress. In otherwords, the value DTEI is fixed upon entering the inertia-phase control.

[0175] As regards the torque converter torque ratio KTR, as shown in atime chart of FIG. 34, in case that the actual KTR is used when theshift is in progress, if the actual KTR increases, the input torque TTAPincrease. As a result, since the control pressure is increased, theshift shock becomes greater. In view of this, the system is configurednot to increase KTR when the shift is in progress (i.e., to change onlyin a direction in which the KTR decreases), thereby enhancing thetracking performance towards a desired G in the inertia-phase control(explained later).

[0176] Based on the above, the calculation of the estimated input torque(engine torque) TTAP will be explained with reference to a flow chart ofFIG. 35.

[0177] The program begins in S1100 in which the aforesaid engine torqueTEPB is retrieved from the mapped data using the detected engine speedNE and the absolute manifold pressure PBA as address data, and proceedsto S1102 in which the value DTEI is calculated.

[0178]FIG. 36 is a flow chart showing the subroutine for thecalculation.

[0179] The program begins in S1200 in which it is determined whether theengine E stalls by an appropriate manner and when the result isaffirmative, the program proceeds to S1202 in which a counter isinitialized. The counter has ten ring buffers which store the detectedengine speed NE successively each time the program is looped (at every10 msec). The program then proceeds to S1204 in which an engine speedchange amount DNE (explained later) is reset to 0.

[0180] When the result in S1200 is negative, the program proceeds toS1206 in which it is determined whether the ten ring buffers of thecounter are filled with the engine speed data and when the result isaffirmative, the program proceeds to S1208 in which an engine speedNEBUFn (detected and stored in any of the buffer at 100 msec earlier) issubtracted from the engine speed NE (detected in the current programloop) to determine the difference therebetween as the engine speedchange amount DNE. When the result in S1206 is negative, the programskips S1208.

[0181] The program then proceeds to S1210 in which the engine speed NE(detected in the current program loop) is stored in any of buffer and toS1212 in which the torque converter slip ratio ETR is calculated byobtaining a ratio between the detected engine speed NE and the inputshaft rotation speed NM and it is determined whether the ratio isgreater than 1.0.

[0182] When the result in S1212 is affirmative, the program proceeds toS1214 in which the value DTEI is reset to 0. When the result isnegative, on the other hand, the program proceeds to S1216 in which itis determined whether the calculated engine speed change amount DNE isless than 0. When the result in S1216 is affirmative, the programproceeds to S1214. When the result is negative, the program proceeds toS1218 in which a predetermined value #KDTEIX is multiplied by the enginespeed change amount DNE to determine the value DTEI.

[0183] The program then proceeds to S1220 in which it is determinedwhether the value of a timer tST is 0. Since the value of the timer isreset to 0 when the shift is in progress in a routine (not shown), theprocessing in S1220 amounts for determining whether the shift is inprogress. When the result in S1220 is negative, the program isimmediately terminated, i.e., the value DTEI is held during shift. Whenthe result is affirmative, the program proceeds to S1222 in which aweighted average between the current value and the preceding value iscalculated using a weight coefficient #NDTEI to smooth or average thevalue DTEI.

[0184] Returning to the explanation of the flow chart of FIG. 35, theprogram proceeds to S1104 in which the torque converter torque ratio KTRis retrieved from a table using the calculated slip ratio ETR as addressdatum, as illustrated in FIG. 33. The program then proceeds to S1106 inwhich it is determined whether the retrieved engine torque TEPB isgreater than 0.

[0185] When the result in S1106 is affirmative, the program proceeds to1108 in which it is determined whether TEPB is greater than DTEI and ifthe result is affirmative, the program proceeds to S1110 in which DTEIis subtracted from TEPB and the obtained difference is multiplied byKTR. The product is named TEPBK. When the result in S1106 or S1108 isnegative, the program proceeds to S112 in which TEPB is renamed TEPBK.The value TEBPK is a value for calculating the engine torque in apower-on-downshift control.

[0186] The program then proceeds to S1114 in which it is determinedwhether the shift is in progress from the value of the timer tST andwhen the result is affirmative, the program proceeds to S1116 in whichKTR is rewritten as KTRLAT. When the result is negative, the programproceeds to S1118 in which it is determined whether KTR is less thanKTRLAT and when the result is affirmative, the program proceeds to S1120in which KTR is rewritten as KTRLAT. When the result is negative, theprogram proceeds to S1122.

[0187] As illustrated in FIG. 33, these are for the calculation of theengine torque for the upshift control. Although KTR and TTAP are shownas KTRLAT and TTAPL in FIGS. 33 and 35, since the operation of thesystem is explained taking the upshift as an example, KTR is the same asKTRLAT and TTAP is the same as TTAPL.

[0188] The program then proceeds to S1122 in which it is determinedwhether TEPB is greater than 0 and when the result is affirmative, theprogram proceeds to S1126 in which it is determined whether TEPB isgreater than DTEI. When the result is negative, the program proceeds toS1124. When the result is affirmative, the program proceeds to S1128 inwhich TTAP is calculated along the manner shown there.

[0189] The program then proceeds to S1130 in which it is determinedwhether the value of QATNUM is 1 * h and the value of SFTMON is greateror equal to 30 h. When the result is negative, since this indicates thatit is under the torque-phase, the program proceeds to S1132 in which NEis rewritten as NEL and latched.

[0190] The program then proceeds to S1134 in which TEPBL is retrievefrom mapped data using the latched engine speed NEL and the manifoldabsolute pressure PBA as address data, as illustrated in FIG. 33. Theprogram then proceeds to S1136 in which it is determined whether theretrieved value TEPBL is greater than 0 and when the result is negative,the program proceeds to S1138 in which TEPBL is determined as TTAPL.

[0191] On the other hand, when the result in S1136 is affirmative, theprogram proceeds to S1140 in which it is determined whether TEBPL isgreater than DTEI and when the result is negative, the program proceedsto S1138. When the result is affirmative, the program proceeds to S1142in which TTAPL is calculated along the manner shown there.

[0192] Thus, as illustrated in FIG. 33, the engine speed NE for mapretrieval is latched when entered the inertia-phase control in theupshift, the estimated input torque is calculated separately for theupshift and the downshift (particularly in the power-on downshift, i.e.,the kick-down). As mentioned above, TTAPL and TTAP are equivalent.

[0193] Returning to the explanation of the flow chart of FIG. 3, theprogram proceeds to S132 in which the aforesaid G1 torque, G2 torque andG3 torque at the ON-side in the inertia-phase are calculated.

[0194]FIG. 37 is a flow chart showing the subroutine for thecalculation.

[0195] Before entering the explanation, however, the calculation will beexplained with reference to FIGS. 38 to 40.

[0196] As mentioned above, the prior art (Japanese Laid-Open PatentApplication No. Hei 6 (1994) - 207660) teaches increasing the hydraulicpressure in upshifting until the drive force becomes equal to that atthe current gear now being engaged and is then kept for a predeterminedperiod. However, since the drive force acting about the vehicle driveshaft is not the same as the acceleration of gravity G acting on theentire vehicle in the linear direction or in the direction of gravity.With this, by controlling drive force to that at the current gear, theshock of the entire vehicle, as a whole, may sometimes become greatercontrary to what is expected.

[0197] Specifically, depending upon the vehicle operating conditions,the torque raised from a dropped level during the torque-phase maygenerate acceleration at the vehicle not only in the vehicle lineardirection, but also in the direction of gravity (i.e. pitching), whichgenerates an increased shock experienced by the vehicle occupant.

[0198] Moreover, although G must happen to absorb the inertia torque ofthe engine E when the engine speed changes, as illustrated in FIG. 38,it is not preferable that G exceeds the level generated at the currentgear.

[0199] In view of the above, the system is configured to predetermine adesired G before and after the inertia-phase, more specifically, bydefining the desired G by a ratio kGUIAn (n: approximately one time tothree times as shown in FIG. 29C) with the use of the estimated inputtoque TTAP (TTAPL) and the gear ratios #RATIOn, #RATIOm before and afterthe shift, and determines the clutch torque (manipulated variable) basedthereon.

[0200] More specifically, defining G at the current gear as 1 (upperlimit) and that at the target gear as 0 (lower limit), the system usesthe ratio kGUIAn (predetermined value) determined between 1 and 0, thesystem determines the clutch torque based on the ratio and the estimatedinput torque, etc., thereby decreasing the shift shock effectively so asto enhance the comfort experienced by the vehicle occupant.

[0201] Explaining this more concretely, in upshifting, the system setsthe desired G, shown as wave-form in FIG. 39. Defining the height of Gat the current gear (1st in this case) as 1 and that at the target gear(2nd in this case) as 0, as illustrated in FIGS. 39A and 39B, the systemdetermined the desired G in the range of 0.3 to 0.7 as illustrated inFIG. 39C. With this, the system can conduct the control such that theshock removal and the shift time (in other words, the clutch load) arewell balanced.

[0202]FIG. 40 is a time chart showing the control entirely. In thefigure, a value corresponding to the estimated input torque TTAPindicates the height o (kGUIA1=0).

[0203] When expressing the clutch torque(s) in equation, it will be asfollows:

[0204] clutch torque at the front portion of inertia-phase

TQONL=TTAP * {1+kGUIA1* ((#RATIOn/#RATIOm)−1)}

[0205] clutch torque at the mid portion of inertia-phase

TQON2=TTAP * {1+kGUIA2 * ((#RATIOn/#RATIOm)−1)}

[0206] clutch torque at the rear portion of inertia-phase

TQON3=TTAP * {1+kGUIA3 * ((#RATIOn/#RATIOm)−1)}

[0207] In the above, #RATIOn: gear reduction ratio in the current gear;#RATIOm; gear reduction ratio in the target gear.

[0208] Thus, the system is configured to determine or calculate theclutch torque based on the clutch torque(s) TQON1, TQON2 and TQON3.

[0209] In the above, the desired G can be set or predetermined in anyshape of wave-form. It may be to be linear in the inertia-phase andecreases in the inertia-phase. For example, when it is thus intended toset the desired G in the form which decreases in the right direction inthe figure with respect to time, for example, it suffices if the ratiokGUIA1 is set to be greater, while the ratio kGUIA2 or kGUIA3 is set besmaller. It can be set more finely if the number of ratios areincreased.

[0210] The ratio kGUIAn is prepared as mapped data to be retrievable bythe vehicle speed V and the throttle opening TH, separately for theshift mode such as upshifting from 1st to 2nd, upshifting from 2nd to3rd (as explained in S808 to S810 in the flow chart of FIG. 27). Itshould be preferable to set the ratio in such a manner that, taking thethermal load of the clutches, the ratio increases with increasingthrottle opening TH.

[0211] Based on the above, the calculation of the G1 torque, etc. willbe explained with reference to the flow chart of FIG. 37.

[0212] The program begins in S1300 in which an inertia-phase switchingslip rate gruia2 is calculated by adding a predetermined value #dGRUIA2to a current-gear clutch slip ratio GRATIO(GA). FIG. 41 illustrates theinertia-phase switching slip ratio gruia2. The clutch slip ratioGRATIO(GA) is obtained by multiplying the clutch slip ratio GRATIO(=NM/NC) by the gear reduction ratio and is corresponding to that at thecurrent gear (GA).

[0213] The program proceeds to S1302 in which it is determined whetherthe clutch slip ratio GRATIO is less than the inertia-phase switchingslip ratio gruia2 and when the result is affirmative, since thisindicates that it is at the front portion of the inertia-phase, theprogram proceeds to S1304 in which the G1 torque TQUIA1 is calculated.

[0214] As mentioned with reference to S808 to S810 in the flow chart ofFIG. 27, the G1 torque TUQUIA1 is calculated by multiplying theestimated input torque TTAP by the ratio #kGUIA1 (correctioncoefficient; obtained based on kGUIA1 by map-retrieval by the throttleopening TH and the fixed vehicle speed VUTA).

[0215] Returning to the explanation of the flow chart of FIG. 37, theprogram the proceeds to S1306 in which the G2 torque TQUIA2 iscalculated.

[0216]FIG. 42 is a flow chart showing the subroutine for thecalculation.

[0217] The program begins in S1400 and proceeds up to S1408 to calculatethe G2 torque TQUIA2 in the same manner as that of the G1 torque TQUIA1explained with reference to FIG. 27, except for using a second ratio#kGUIA2 (correction coefficient; obtained based on kGUIA2 bymap-retrieval by the throttle opening TH and the fixed vehicle speedVUTA) corresponding to the G2 torque TQUIA2.

[0218] Again returning to explanation of the flow chart of FIG. 37, theprogram proceeds to S1308 in which, by interpolating the calculated G1torque TQUIA1 and G2 torque TQUIA2, the ON-side desired clutch torqueTQON therebetween is calculated.

[0219] When the result in S1302 is negative, the program proceeds toS1310 in which the G2 torque TQUIA2 is calculated in the mannermentioned above, and to S1312 in which a G3 torque TQUIA3 is calculated.

[0220]FIG. 43 is a flow chart showing the subroutine for thecalculation.

[0221] The program begins in S1500 and proceeds up to S1508 to calculatethe G3 torque TQUIA3 in the same manner as that of the G1 torque TQUIA1explained with reference to FIG. 27, except for using a third ratio#kGUIA3 (correction coefficient; obtained based on kGUIA3 bymap-retrieval by the throttle opening TH and the fixed vehicle speedVUTA) corresponding to the G3 torque TQUIA3.

[0222] Again returning to explanation of the flow chart of FIG. 37, theprogram proceeds to S1314 in which, by interpolating the calculated G2torque TQUIA2 and G3 torque TQUIA3, the ON-side desired clutch torqueTQON therebetween is calculated.

[0223] Having been configured in the foregoing manner, the systemaccording to the embodiment can determine the characteristics of controlas desired and can decrease the shift shock effectively. Further, sincethe system determines the manipulated variable using the estimated inputtorque as the parameter indicative of the engine toque, it can preventfrom the clutch capacity from being disadvantageously balanced with theengine torque and can accordingly avoid the disadvantage in that theshifting is unnecessarily elongated such that the shifting does notfinish in an expected period of time.

[0224] Again returning to the explanation of the flow chart of FIG. 3,the program proceeds to S134 in which the OFF-side desired clutch torqueTQOF in the inertia-phase is set to 0, to S136 in which the ON-sideclutch pressure QATON is calculated based on the calculated ON-sidedesired clutch toque TQON in the inertia-phase in accordance with thetorque-pressure conversion explained below and generates a command valueto the shift solenoid(s) SLn concerned based on the calculated ON-sideclutch pressure QATON.

[0225] The program then proceeds to S138 in which the OFF-side clutchpressure QATOF is calculated based on the set OFF-side desired clutchtoque TQOF in the inertia-phase in accordance with the torque-pressureconversion explained below and generates a command value to the shiftsolenoid(s) SLn concerned based on the calculated OFF-side clutchpressure QATOF.

[0226] In the next program, the result in S126 is normally negative, andthe program proceeds to S140 in which it is determined whether the valueof SFTMON is 30 h or 31 h and when the result is affirmative, theprogram proceeds to S142 in which it is determined whether the clutchslip ratio GRATIO is greater than a predetermined value #GRUEAG. Thepredetermined value #GRUEAG is a threshold value in clutch slip rate todetermine starting of the engage control. The processing in S142 amountsfor determining whether the shift is so close to the completion that theengage control should be started.

[0227] When the result in S142 is negative, the program proceeds toS132. When the result in S142 is affirmative, on the other hand, theprogram proceeds to S144 in which the value of SFTMON is set to 40 h.The program then proceeds to S146 in which an ON-side engaging pressureas the ON-side clutch pressure QATON (i.e. the torque-pressure convertedvalue) is calculated based on the ON-side desired clutch torque TQON.

[0228]FIG. 44 is a flow chart showing the subroutine for thecalculation, more precisely the torque-pressure conversion.

[0229] Before entering the explanation thereof, however, the calculationof the torque-pressure conversion in the inertia-phase in the systemaccording to the embodiment will be outlined.

[0230] In converting the torque value to the hydraulic pressure value,the converted pressure value has usually been corrected by the ATFtemperature. However, disadvantageously, the characteristic of thetemperature correction has not been uniform. Further, the otherparameters such as the vehicle speed V (in other words., the rotationaldifference) and throttle opening TH (in other words, the hydraulicpressure) should also be taken into account.

[0231] In view of the above, the system according to the embodiment isconfigured to determine the Sommerfeld number (dimensionless number)based on the viscosity of ATF and the surface pressure of the hydraulicclutch (Cn), to estimate the clutch friction coefficient μ, and toconduct the torque-pressure conversion based on the estimated clutchfriction coefficient. This is the same in the torque-pressure conversionin the torque-phase.

[0232] This will be explained in detail.

[0233] Although the frictional characteristics (μ characteristic) of theclutch disk of the hydraulic clutch (Cn) vary with the rotationaldifference between the clutch disk and the pressure plate facingthereto, the ATF temperature TATF and the clutch disk surface pressure,the followings are generally known.

[0234] 1. The clutch disk friction coefficient μ (more precisely dynamicfriction coefficient μd) tends to decrease as the rotational difference(peripheral speed difference) between the clutch disk and the pressureplate decreases.

[0235] 2. The clutch disk dynamic friction coefficient μd tends toincrease as the shearing force of the hydraulic oil increases, since theATF viscosity raises when the ATF temperature drops.

[0236] 3. The clutch disk dynamic friction coefficient μd tends todecrease as the surface pressure of the clutch disk increases.

[0237] Since the clutch disk dynamic friction coefficient μd is actuallydetermined by the mutual influences of these three characteristics, thesystem is configured to predetermine a parameter S(indicative of thequantity of state, i.e. the Sommerfeld number) as the clutch diskdynamic friction coefficient through experimentation based on therotational difference between the clutch disk and the pressure plate,the ATF temperature and the clutch disk surface pressure, and to storethe same in a memory of the ROM 84 of the ECU 80.

[0238] The parameter S(i.e. Sommerfeld number) can be expressed in aequation as follows:

S=ATF viscosity*peripheral speed/clutch disk surface pressure

[0239] In the inertia-phase in upshifting, since the ON-side clutchtorque is immediately reflected to the output shaft torque, in order todecrease the shift shock, it becomes necessary to control the ON-sidedesired clutch torque TQON. The ON-side desired clutch torque TQON isgenerally expressed as follows:

[0240] TQON=μ* clutch disk numbers * clutch diameter * (clutchpressure * piston's pressure-receiving area+hydraulic pressurecentrifugal force component return spring force)

[0241] Among of all, the clutch disk friction coefficient μ, moreprecisely clutch disk dynamic friction coefficient μd varies with theconditions. Accordingly, in order to suppress the shift shock, it issignificant to determine the coefficient μd accurately. In view of theabove, the system is configured to calculate the clutch disk dynamicfriction coefficient μd on a real-time basis using the parameter S todetermine the ON-side clutch pressure QATON, thereby ensuring to outputthe clutch torque as desired.

[0242] To be more specific, by controlling the actual pressure to besupplied to the clutch based on the calculated ON-side clutch pressureQATON, it becomes possible to obtain a uniform G wave-formirrespectively of the rotational difference between the clutch disk andthe pressure plate, the ATF temperature and the clutch disk surfacepressure, thereby ensuring to decrease or suppress the shift shockeffectively.

[0243] Explaining this with reference to FIGS. 45A to 45D, the systemcontrol to start the shifting from a point where Sis relatively small ifthe ATF temperature is relatively high, as illustrated in FIG. 45A, andto start the shifting from a point where Sis relatively great if the ATFtemperature is relatively low, as illustrated in FIG. 45B. FIG. 45Cillustrates the change of the friction coefficient with respect to timeat high ATF temperature and FIG. 45D illustrates that at low ATFtemperature. Thus, by controlling the clutch hydraulic pressure bytaking the change of the friction coefficient into account, it becomespossible to obtain a more uniform wave-form of G.

[0244] Based on the above, the torque-pressure conversion will beexplained with respect to the ON-side clutch torque referring to theflow chart of FIG. 44. FIG. 46 is a block diagram similarly showing theconversion.

[0245] The program begins in S1600 in which it is determined whether thecalculated desired clutch torque TQON is less than 0, in other words, itis determined whether the value is a negative value. When the result isaffirmative, the program proceeds to S1602 in which the desired clutchtorque TQON is determined to be 0.

[0246] The program then proceeds to S1604 in which it is determinedwhether the bit of a flag f.MYUON is set to 1. Since the bit of the flagis set to 1 in a routine (not shown) when the shift control is started,the determination in S1604 amounts for determining whether it is for thefirst program loop in the shift control.

[0247] When the result in S1604 is affirmative, the program proceeds toS1606 in which the bit of the flag is reset to 0, to S1608 in which theclutch disk friction coefficient μ is set to its initial value #μDcn,since the calculation of the parameter S requires the value of μ. Whenthe result in S1604 is negative, the program proceeds to S1610 in whichthe preceding value of μn (the value at the program loop n time(s)earlier) is renamed as μ(i.e. current value).

[0248] The program then proceeds to S1612 in which the rotationaldifference dnm.nc based on the input shaft rotational speed NM, theoutput shaft rotational speed NC and the gear reduction ratio #RATIOn,and to S1614 in which the parameter S (Sommerfeld number) is calculated.The parameter is calculated by multiplying the rotational differencednm.nc by the ATF viscosity η, the friction coefficient μ and aSommerfeld number calculation coefficient KZOM to obtain a pruduct andby dividing the obtained product by the desired clutch torque TQON. Asmentioned above, the initial value or the preceding value is used as μ.

[0249] More specifically, the parameter Sis calculated as follows:

[0250]  S=(η*dnm.nc)/Pdisk

[0251]

[0252] In the above, the ATF viscosity η is prepared as table data to beretrieved by the detected ATF temperature. Pdisk indicates the clutchdisk surface pressure and is calculated as follows:

Pdisk=TQON/(KZOM*μ)

[0253] The program proceeds to S1616 in which the clutch disk dynamicfriction coefficient μd is retrieved from table data using the parameterS as address datum, and to S1618 in which a value FDISK (indicative ofthe disk pressing force by hydraulic pressure) is calculated by dividingthe ON-side desired clutch torque TQON by a product obtain bymultiplying a coefficient KDISK by the friction coefficient μd. Thecoefficient KDISK is a value prepared differently or separately for theclutches to be used for calculating the value FDISK from the ON-sidedesired clutch torque TQON.

[0254] The program proceeds to S1620 in which a value Fctf (indicativeof the hydraulic pressure centrifugal force component acting on theclutch drum) is subtracted from the value FDISK, but a value Frtn(indicative of the aforesaid the return spring force) is added, and bydividing the obtained value is divided by a value Apis (indicative ofthe aforesaid piston's pressure-receiving area) to determine thequotient as the ON-side clutch pressure QATON. The value Fctf isobtained by retrieving table data by the input shaft rotational speedNM.

[0255] Again returning to the flow chart of FIG. 3, the program proceedsto S148 in which the OFF-side engage pressure is calculated ordetermined as the OFF-side clutch pressure QATOF in the manner similarto the above.

[0256]FIG. 47 is a flow chart showing the subroutine for thecalculation.

[0257] The program begins in S1700 in which it is determined whether thecalculated OFF-side desired clutch toque TQOF is less than 0, in otherwords, it is determined whether TQOF is a negative value and when theresult is affirmative, the program proceeds to S1702 in which theOFF-side desired clutch torque TQOF is determined to be 0.

[0258] The program then proceeds to S1704 in which it is determinedwhether the value of the shift mode QATNUM is 2 * h, in other words, itis determined whether the shift is the downshift and when the result isnegative, the program proceeds to S1706 in which the bit of a flagf.MYUOF (similar to f.MYON) is reset to 0, and to S1708 in which thefriction coefficient μd is set to be a predetermined value #μSCn(corresponding to static friction coefficient), since the main purposeof the OFF-side pressure control in upshifting is prevent the clutchfrom slipping.

[0259] When the result in S1704 is affirmative, since this indicatesthat the shift is the downshift, the program proceeds to S1710 in whichit is determined whether the bit of the flag f.MYUOF is set to 1 andwhen the result is affirmative, the program proceeds to S1712 in whichthe bit of the flag is reset to 0, and to S1714 in which the frictioncoefficient μ is set to be an initial value #μDcn. When the result inS1710 is negative, the program proceeds to S1716 in which the precedingvalue of μn (the value at the program loop n time(s) earlier) is renamedas μ (i.e. current value).

[0260] The program then proceeds to S1718 in which a clutch rotationaldifference domega is set to be a constant value #dOMEGA. The programthen proceeds to 1720 in which the parameter S (Sommerfeld number) iscalculated similar to the calculation of the ON-side value, to S1722 inwhich the dynamic friction coefficient μd is retrieved from table datausing the parameter S as address datum, to S1724 in which the valueFDISK is calculated, and to S1726 in which the clutch pressure QATOF iscalculated as shown there.

[0261] Again returning to the flow chart of FIG. 3, when the result inS140 is negative, the program proceeds to S150 in which it is determinedwhether the value of the timer tUEAG has reached 0 and when the resultis negative, the program proceeds to S146. On the other hand, when theresult is affirmative, the program proceeds to S152 in which theparameters are reset to zero and other processing necessary forfinishing is conducted.

[0262] As mentioned above, the embodiment of the invention is configuredto have a system for controlling an automatic transmission (T) of avehicle (1) having an input shaft (MS) connected to an internalcombustion engine (E) mounted on the vehicle and an output shaft (CS)connected to driven wheels (W) of the vehicle, the transmissiontransmitting input torque, through any of frictional engaging elements(Cn), generated by the engine and inputted by the input shaft to thedriven wheels by the output shaft, in accordance with predeterminedshift scheduling (S10) defining a target gear (SH, GB) based on detectedoperating conditions of the vehicle and the engine, including; hydraulicpressure calculating means (80, S20, S110, S300-S308, S402) forcalculating hydraulic pressure to be supplied to the frictional engagingelements (Cn); and hydraulic pressure control circuit (O) for supplyinghydraulic pressure to the frictional engaging elements based on at leastthe calculated hydraulic pressure. The characteristic features of thesystem are that the system includes: input shaft rotational speeddetecting means (64, 80) for detecting an input shaft rotational speed(NM) inputted to the transmission; supply time determining means (80,S20, S110, S300-S308, S400-S406) for determining a supply time ((actual)preparation-completion time T1, T) to supply a preparatory pressure toone of the frictional engaging elements (Cn) of the target gear (GB) tobe shifted to, based on at least the detected input shaft rotationalspeed (NM), when shift is to be conducted (SFT MON=0); oil amountestimating means (80, S20, S110, S300-S308, S404, S500-S544) forestimating an oil amount (OILn) in the one of the frictional engagingelements (Cn); and supply time correcting means (80, S20, S110, S406)for correcting the supply time (T1, T) based on the estimated oil amount(OILn); and the hydraulic pressure calculating means (80, S20, S110,S300-S308, S402) calculates the preparatory pressure (QDB1A (QATON)) tobe supplied to the one of the frictional engaging elements (Cn) withinthe determined supply time. With this, it becomes possible to effect theclutch-stroke play removal within a less variant period of time and witha good response, thereby decreasing the shift shock effectively so as toimprove the feeling of the vehicle occupant. Further, by correcting thetime by the estimated oil amount, it becomes possible to effect theclutch-stroke play removal appropriately even when the shift occurssuccessively.

[0263] In the system, the hydraulic pressure calculating meanscalculates the preparatory pressure (QDB1A (QATON)) based on at leastthe detected input shaft rotational speed (NM; 80, S20, S110, S300-S308,S402). With this, it becomes possible to effect the clutch-stroke playremoval within a lesser variant period of time and with a betterresponse, thereby decreasing the shift shock more effectively so as toimprove the feeling of the vehicle occupant.

[0264] In the system, the oil amount estimating means includes; residualoil amount estimating means (80, S20, S110, S300-S308, S404, S506, S524)for estimating a residual oil amount (OILn) in the one of the frictionalengaging elements; and oil decreasing amount estimating means (80, S20,S110, S300-S308, S404, S510, S524) for estimating an oil decreasingamount decreasing from the one of the frictional engaging elements basedon at least the estimated residual oil amount and the detected inputshaft rotational speed, and estimates the oil amount (OILn) bysubtracting the oil decreasing amount (dOILn) from the residual oilamount (OILn; 80, S20, S110, S300-S308, S404, S512, S526). With this, itbecomes possible to effect the clutch-stroke play removal moreappropriately even when the shift occurs successively.

[0265] In the system, the oil decreasing amount estimating meansestimates the oil decreasing amount based on at least the estimatedresidual oil amount, the detected input shaft rotational speed and alength of passage for supplying and draining pressurized oil (80, S20,S110, S300-S308, S404, S510, S524).

[0266] It should be noted in the above, although the engine torque isestimated or calculated, it is alternative possible to use a torquesensor to determine the engine torque.

[0267] While the invention has thus been shown and described withreference to specific embodiments, it should be noted that the inventionis in no way limited to the details of the described arrangements butchanges and modifications may be made without departing from the scopeof the appended claims.

What is claimed is: (for US, CANADA)
 1. A system for controlling anautomatic transmission of a vehicle having an input shaft connected toan internal combustion engine mounted on the vehicle and an output shaftconnected to driven wheels of the vehicle, the transmission transmittinginput torque, through any of frictional engaging elements, generated bythe engine and inputted by the input shaft to the driven wheels by theoutput shaft, in accordance with predetermined shift scheduling defininga target gear based on detected operating conditions of the vehicle andthe engine, comprising; input shaft rotational speed detecting means fordetecting an input shaft rotational speed inputted to the transmission;supply time determining means for determining a supply time to supply apreparatory pressure to one of the frictional engaging elements of thetarget gear to be shifted to, based on at least the detected input shaftrotational speed; oil amount estimating means for estimating an oilamount in the one of the frictional engaging elements; supply timecorrecting means for correcting the supply time based on the estimatedoil amount; preparatory pressure calculating means for calculating thepreparatory pressure to be supplied to the one of the frictionalengaging elements within the determined supply time; and hydraulicpressure control circuit for supplying the preparatory pressure to theone of the frictional engaging elements based on the calculatedpreparatory pressure.
 2. A system according to claim 1 , wherein thepreparatory pressure calculating means calculates the preparatorypressure based on at least the detected input shaft rotational speed. 3.A system according to claim 1 , wherein the oil amount estimating meansincludes; residual oil amount estimating means for estimating a residualoil amount in the one of the frictional engaging elements; and oildecreasing amount estimating means for estimating an oil decreasingamount decreasing from the one of the frictional engaging elements basedon at least the estimated residual oil amount and the detected inputshaft rotational speed, and estimates the oil amount by subtracting theoil decreasing amount from the residual oil amount.
 4. A systemaccording to claim 2 , wherein the oil amount estimating means includes;residual oil amount estimating means for estimating a residual oilamount in the one of the frictional engaging elements; and oildecreasing amount estimating means for estimating an oil decreasingamount decreasing from the one of the frictional engaging elements basedon at least the estimated residual oil amount and the detected inputshaft rotational speed, and estimates the oil amount by subtracting theoil decreasing amount from the residual oil amount.
 5. A systemaccording to claim 3 , wherein the oil decreasing amount estimatingmeans estimates the oil decreasing amount based on at least theestimated residual oil amount, the detected input shaft rotational speedand a length of passage for supplying and draining pressurized oil.
 6. Asystem according to claim 4 , wherein the oil decreasing amountestimating means estimates the oil decreasing amount based on at leastthe estimated residual oil amount, the detected input shaft rotationalspeed and a length of passage for supplying and draining pressurizedoil.
 7. A method of controlling an automatic transmission of a vehiclehaving an input shaft connected to an internal combustion engine mountedon the vehicle and an output shaft connected to driven wheels of thevehicle, the transmission transmitting input torque, through any offrictional engaging elements, generated by the engine and inputted bythe input shaft to the driven wheels by the output shaft, in accordancewith predetermined shift scheduling defining a target gear based ondetected operating conditions of the vehicle and the engine, comprisingthe steps of; (a) detecting an input shaft rotational speed inputted tothe transmission; (b) determining a supply time to supply a preparatorypressure to one of the frictional engaging elements of the target gearto be shifted to, based on at least the detected input shaft rotationalspeed; (c) estimating an oil amount in the one of the frictionalengaging elements; (d) correcting the supply time based on the estimatedoil amount; (e) calculating the preparatory pressure to be supplied tothe one of the frictional engaging elements within the determined supplytime; and (f) supplying the preparatory pressure to the one of thefrictional engaging elements based on the calculated preparatorypressure.
 8. A method according to claim 7 , wherein the step (e)calculates the preparatory pressure based on at least the detected inputshaft rotational speed.
 9. A method according to claim 7 , wherein thestep (c) includes the steps of; (g) estimating a residual oil amount inthe one of the frictional engaging elements; and (h) estimating an oildecreasing amount decreasing from the one of the frictional engagingelements based on at least the estimated residual oil amount and thedetected input shaft rotational speed, and estimates the oil amount bysubtracting the oil decreasing amount from the residual oil amount. 10.A method according to claim 8 , wherein the step (c) includes the stepsof; (g) estimating a residual oil amount in the one of the frictionalengaging elements; and (h) estimating an oil decreasing amountdecreasing from the one of the frictional engaging elements based on atleast the estimated residual oil amount and the detected input shaftrotational speed, and estimates the oil amount by subtracting the oildecreasing amount from the residual oil amount.
 11. A method accordingto claim 9 , wherein the step (h) estimates the oil decreasing amountbased on at least the estimated residual oil amount, the detected inputshaft rotational speed and a length of passage for supplying anddraining pressurized oil.
 12. A method according to claim 10 , whereinthe step (h) estimates the oil decreasing amount based on at least theestimated residual oil amount, the detected input shaft rotational speedand a length of passage for supplying and draining pressurized oil.